The most obvious reason is the one that's been cited from the beginning -- he doesn't want to play nose tackle and he thinks the Redskins will force him to play nose tackle. That could be the real reason. In fact, I'm sure it's a big part of it. But I also wonder if there isn't something else.
Haynesworth has taken no part in the Redskins offseason conditioning program and everyone who has followed Haynesworth's career knows he has a tendency to get fat and winded. My hunch is that the nose tackle issue is at the heart of this, but another reason he's not at Redskins Park today is that Fat Albert really is Fat Albert. I wonder how much he weighs right now. I wonder when was the last time he ran a sprint or lifted real weights.